Four more people have been arrested in connection with the case against an Egyptian-American human rights activist, bringing to 10 the number held in the affair, the prosecutor's office said Tuesday.

Four people who work for the Ibn Khaldun Center, which focuses on human rights and democracy issues, were arrested Monday evening after four of their colleagues were arrested earlier in the day, it said.

The center's prominent director, Saad Eddin Ibrahim, was arrested late Friday and charged with receiving funds from abroad to undermine Egypt's stability.

The Ibn Khaldun Center's accountant was also being held without charge for two weeks.

The eight detained on Monday were being questioned about their "involvement in the case of fraudulent electoral cards found on the center's premises," the prosecutor's office said.

Ibrahim faces 15 years in prison if found guilty of the charges, which include drafting reports on the internal situation in Egypt, Morocco, Tunisia and other Arab countries in exchange for money from abroad.

On Monday, the prosecutor's office specifically accused Ibrahim of having instructed researchers at the center to register fictitious names of voters on the cards and paid each one 300 Egyptian pounds (around 90 dollars).

Ibrahim then "received a sum of around 50,000 pounds (14,300 dollars) from the European Union" as part of an EU-sponsored program to educate citizens about their civic rights, the office said.

His family said the charges are groundless.

Friends of the family said they were all the more shocked at Ibrahim's arrest because they described him as a man who tried to bring gradual changes through working from inside the system rather than as a radical from outside.

They added he is an advisor to three ministers.

A US consular official was satisfied with a visit made Monday to Ibrahim, an Egyptian-born US citizen who is being held in a Cairo prison - CAIRO (AFP)